Their research on the natural variability of the Earth’s climate “contextualizes current greenhouse gas concentrations and the associated global warming” within the frame of planetary history, in the words of the award citation. For the committee, the convergent contributions of the five awardees have revealed that “over the past 800,000 years, greenhouse gas concentrations due to natural variability have never reached the atmospheric levels seen today,” the cause of our current human-induced global warming.

Their work, it concludes, “required scientific, technical and logical breakthroughs in many areas to measure greenhouse gas concentrations,” and “has built upon sustained international collaborative efforts by generations of researchers.”

“The main message from the ice sheets is that CO₂ and temperature are tightly coupled; that the amount of greenhouse gases in the atmosphere today is without precedent in the last 800,000 years. And this has profound implications for how our planet will evolve over the coming decades and centuries,” says Bjorn Stevens, committee chair and Director of the Max Planck Institute for Meteorology. “If we want to abate or mitigate warming, it’s quite clear that we have to reduce the concentration of greenhouse gases in the atmosphere.”

“As it gradually accumulates, the snow that forms the polar ice captures the air around it,” explains committee member Miquel Canals, Director of the Sustainable Blue Economy Chair. “This air gets trapped in bubbles within the ice. And these bubbles are like a book on the atmospheric conditions prevailing through time which we need to decipher to get to their composition and meaning.”

The five awardee scientists have, in effect, reconstructed this precious record of the Earth’s climate conserved in the polar ice. “This is fascinating and invaluable work,” Canals continues, “which provides us with a benchmark for the current status of global warming.”

For Joan Grimalt Obrador, a researcher at the Institute of Environmental Assessment and Water Research (IDAEA) of the Spanish National Research Council (CSIC) and nominator of Thomas Stocker, the awardees’ principal achievement has been to demonstrate that today’s greenhouse gas concentrations are definitively off the scale. So we are on uncharted ground, living an experiment whose result is a question mark. And the threat is to human life, not nature, which has always found ways to adapt.”

Conclusive proof on the link between CO₂ and warming

Ice core analysis has been a landmark in climate science, providing conclusive evidence of the linkage between greenhouse gases and the Earth’s temperature. Back in the 1960s, there were already physics-based climate models showing that increased atmospheric concentrations of carbon dioxide would lead to higher temperatures. What was missing was concrete data on the composition of the atmosphere through history that could validate this finding. Jean Jouzel’s analysis of an Antarctic ice core from the Vostok base, published in Nature in 1987, brought the needed confirmation: “The link between changes in greenhouse gases and temperature was really established thanks to that Vostok ice core,” he recalls today.

Although there had been studies done on ice cores, none had reached back further than the last ice age, which began 110,000 years ago. But the Soviet scientists stationed at Vostok managed to drill more than 2,000 meters down through the ice, obtaining samples of an age of up to 160,000 years, i.e., the previous interglacial period. Jouzel and his colleague Claude Lorius, who died in 2023, could get access to these samples thanks to the latter’s contacts with members of the Vostok team, and what the two observed was a close linkage between changes in the carbon cycle, atmospheric composition and climate, three key factors in the dynamics of glacial-interglacial cycles.

‘Time machines’ to establish the climate impact of human activity

Ten years after that Nature article, Valérie Masson-Delmotte elaborated on Jouzel’s work, extending his analysis to Greenland ice cores. Her conclusions matched those obtained by her compatriot at the opposite end of the planet, adding robustness to his findings. Since then, Masson-Delmotte and Jouzel, as well as their fellow awardees, have been working to refine the study of past climates and understand their evolution over hundreds of thousands of years.

“Ice cores are these amazing time machines,” Masson-Delmotte enthuses. “What is really striking is that we are finding ever stronger evidence confirming the intuition from the late 1970s.” And these records also highlight the extent to which atmospheric greenhouse gas levels have rocketed as a consequence of human activity: “The ice core record, together with other sources of information, shows that human influence on the whole climate system is unequivocal,” says the awardee scientist.

As well as modeling past climate with ice cores, Masson-Delmotte has combined this data with multiple other aspects of climate science to predict what the Antarctic will look like in 2070 under different warming scenarios. “We show that if global warming holds at levels close to present day, major changes could be avoided for the region, while with larger degrees of warming, there would be potentially irreversible changes.”

One implication of this warming would be a rise in sea level, which is already 20 centimeters higher than in 1900 and with the rate of increase accelerating since the 1990s. “We are heading for a sea-level rise of 50 cm by 2100 if warming is contained at low levels, and of more than one meter in the event of very high greenhouse gas emissions,” Masson-Delmotte warns. “These rises will affect about one billion people by 2050, with multiple direct consequences for our coasts. In northern France, we have already experienced unmanageable flooding due to exceptionally high rainfall and rising sea levels.” In sum, the results achieved by this group of researchers show that the records preserved in the polar ice testify to phenomena and situations that extend across the whole planet, including the regions furthest from the poles. 

Understanding Greenland’s past to understand the Earth’s future climate

Dorthe Dahl-Jensen’s contributions lie primarily in the reconstruction of past climate from the study of Greenland ice cores, as written up in a 1998 paper published in Science. “The knowledge from the past preserved in ice cores is important for understanding what can happen in the future,” she explains, “because most modeling work is based on instrumental records from weather stations that only reach 150 years back in time, a very stable climate period. And we know from the past that this is not the full story.”

“The ice gives us both temperature, through the analysis and interpretation of stable water isotopes, and greenhouse gas levels, through the air trapped inside,” Dahl-Jensen relates. Her research has found that past temperatures rose during periods of increased solar energy influx, which in turn increased CO₂ in a positive feedback loop: “We know that when temperature rises, it warms the ocean, which releases CO₂ into the atmosphere. These higher levels of CO₂ warm the atmosphere and ocean even more, and then CO₂ starts to rise again. So we get the warming episodes observed in the climate of the past.”

But what Dahl-Jensen’s research has revealed is that greenhouse gas concentrations at no point reached the levels of today. “Even though there have been previous warm periods, like we had 115,000 years ago, where the temperature was actually four degrees warmer, we never saw CO₂ values higher than 300 parts per million, while the average today is 420 ppm. So it is us who have brought about these heightened values of CO₂ that are driving up temperatures.”

This is why she is so concerned about the potential impacts of human-induced global warming, some of which are probably already unstoppable: “We know that CO₂ stays in the atmosphere for more than 100 years, so it’s going to be very hard to stop temperatures rising with the greenhouse gas concentrations we have right now.” In fact, the Danish scientist believes some tipping points have already been passed, like the inevitable disintegration of the large Antarctic ice shelves that is visibly underway.

Dahl-Jensen also points out that, based on the results of her research on abrupt changes in past climate, there is a risk that the pouring of fresh water into the ocean, due to the ice melt, could disrupt the ocean currents that give Europe its relatively mild winters. “The Gulf Stream is important because it warms northern Europe, Denmark and Spain as well. And if it shuts down due to global warming, it will strongly impact climate in our countries, though ironically enough, it will cool the temperature.”

Technological innovation to trace climate history in the ice

None of this research would not have been possible without the technology to obtain ice cores, and here Jakob Schwander has been a pioneer. He refers to himself as “passionate” about engineering and ice drilling techniques. An area in which he is recognized as a brilliant innovator, developing, improving and creating new devices to reach ever deeper layers of pristine ice. This, precisely, has been one of his main contributions.

It was through his inventions that Schwander was able to analyze the air bubbles trapped in the “firn” – the layer of compacted ice at over 70 meters depth that lasts through winter after winter above the level of the glacial ice, and holds 25% of air. In 1984 he published a paper in Nature which concluded that the age of the air trapped in bubbles was significantly less than that of the enclosing ice.

“Thanks to the fact that heavy gases sink to the top layers of the firn, we can now tell the age of the air trapped in the polar ice layers, which do not coincide. This is a process that happens only in porous materials like firn or sand dunes. It doesn’t occur in the atmosphere because the atmosphere is constantly mixed by the wind. This has led to improvements in the construction of ice core age scales at different depths, which has also led to greater accuracy in measuring past temperature and precipitation,” he explains. “My contribution has maybe been to serve as a springboard for other studies. When I started, I was practically on my own. And now there are hundreds of people working on the subject.”

Just over ten years ago, Schwander began work on what would become his signature innovation, the world’s smallest ice drill, with a diameter of just 2 cm. Known as the RADIX (Rapid Access Drill for Ice eXtraction), in 2021 it reached a depth of 320 meters (-55º) in the Antarctic ice, a task completed in a few short days. “It’s a completely new technique,” Schwander points out. “Many parts of the drill had to be redesigned to make them small enough.”

New models for a “unique knowledge” of our planet

Thomas Stocker, who worked with Schwander on the RADIX project, has measured concentrations of carbon dioxide trapped in the air bubbles of ice cores extending back 800,000 years. Seeking to interpret the data found, he developed a number of climate models to understand climate changes over a very long time scale spanning several ice ages.

He drew three main conclusions from this research. “First of all, carbon dioxide concentrations today are 35% higher than at any time in the past 800,000 years. Second, warming is without precedent in at least the last 2,000 years. And third, we have learned from polar ice cores that there are instabilities in the climate system, abrupt changes that could actually happen again in the future due to the large perturbations that man is inflicting on climate.”

The researcher insists that an important part of these findings is that they draw on data from both Antarctica and Greenland, providing “unique knowledge” about the dynamics of the Earth system. Abrupt changes in past climate indicate that the coupled system of the atmosphere and ocean have “limited stability” to perturbations, with the ocean being an important element in communicating large-scale climate disruptions between the hemispheres. Stocker points out that this had first been hypothesized based on model simulations, but “could then be confirmed by the precise analysis of ice cores from Greenland and Antarctica.”

The gap between the scientific evidence and political inaction in addressing the climate challenge

All five laureates believe there is a worrying gap between the unequivocal scientific evidence on the potential impacts of today’s climate change and the so far inadequate response of the international community. They also believe, however, that there remains room for maneuver in dealing with the challenge.

“We are still dragging our feet, although in most countries there is a growing awareness of the need to act,” Dahl-Jensen contends. “We have time, but if we wait, the consequences will be more severe, because greenhouse gases are still warming the planet and will continue to do so for the next 100 years, even if we halt emissions. So we need to react now and start reducing our use of fossil fuels.”

“For the moment it seems that we are not able to reach the goals we have set to tackle climate change,” says Schwander. “Probably because humans are not suffering enough yet. So I think to solve the problem we have to improve our energy efficiency and use of resources, and here we can learn a lot from nature. Nature is very efficient at using resources and recycling, and in the use of energy.”

“My impression is that the scientific community has done its work, in the sense that we have alerted policymakers to the gravity of the situation. But the real challenge is then to turn these recommendations into real and effective measures,” says Jouzel.

“It’s not about hope or despair,” adds Masson-Delmotte, “It’s a matter of effective action. When you find yourself with your back against the wall, when you are faced with extreme events like those experienced in Spain with fires, intense heat waves or heavy rainfall, what you need is not to resign yourself, but to step up the action.”

For Stocker “science identified the problem of climate change as early as the late 1970s, but the response of the public and the policymakers has been extremely slow. The time to act is now, and to act means to reduce greenhouse gas emissions as urgently as possible to keep within the temperature bands stated in the Paris Agreement of 2015, which means keeping global warming well within two degrees celsius. Inaction may mean short-term benefits but also long-term damages: conflicts between communities and between nations over resources like water and living space.”

Nominators

A total of 67 nominations were received in this edition. The awardee researchers were nominated by Sune O. Rasmussen and Anders Svensson, University of Copenhagen (Denmark); James W. C. White, University of Colorado Boulder (United States); Philippe Bousquet, CEA Orme des Merisiers (French Alternative Energies and Atomic Energy Commission), France; Hubertus Fischer, Thomas F. Stocker and Nicolas Thomas, University of Bern (Switzerland) and Joan Grimalt Obrador, Spanish National Research Council (Spain).

Climate Change committee and evaluation support panel

The committee in this category was chaired by Bjorn Stevens, Director of the Max Planck Institute for Meteorology (Hamburg, Germany), with Carlos Duarte, holder of the Tarek Ahmed Juffali Research Chair in Red Sea Ecology at King Abdullah University of Science and Technology (Thuwal, Saudi Arabia), acting as secretary. Remaining members were Sandrine Bony, Director of Research in the Laboratoire de Météorologie Dynamique (LMD) at Sorbonne University (Paris, France); Miquel Canals, Director of the Sustainable Blue Economy Chair and and Professor of Marine Geosciences in the Department of Earth and Ocean Dynamics at the University of Barcelona (Spain); José Manuel Gutiérrez, Director of the Institute of Physics of Cantabria (IFCA) and Coordinating Lead Author of the Atlas chapter in the IPCC’s Sixth Assessment Report; Martin Heimann, Director Emeritus in the Department of Biogeochemical Systems at the Max Planck Institute for Biogeochemistry (Jena, Germany); Edward Rubin, Alumni Chair Professor of Environmental Engineering and Science Emeritus at Carnegie Mellon University (Pittsburgh, United States); Paul Wassmann, Professor Emeritus in the Department of Arctic and Marine Biology at UiT The Arctic University of Norway; and Julie Winkler, Professor of Geography in the Department of Geography, Environment and Spatial Sciences of Michigan State University (United States).

The evaluation support panel of the Spanish National Research Council (CSIC) was coordinated by Teresa Moreno Pérez, Deputy Coordinator of the LIFE Global Area and Research Professor at the Institute of Environmental Assessment and Water Research (IDAEA, CSIC), and formed by Josep M. Gasol Piqué, Research Professor at the Institute of Marine Sciences (ICM, CSIC), Guillermo Gea Izquierdo, Scientific Researcher at the National Institute for Agricultural and Food Research and Technology (INIA, CSIC); Francisca Martínez Ruiz, Scientific Researcher at the Andalusian Earth Sciences Institute (IACT, CSIC-UGR); and Sergio Vicente Serrano, Research Professor at the Pyrenean Institute of Ecology (IPE, CSIC).

About the BBVA Foundation Frontiers of Knowledge Awards

The BBVA Foundation centers its activity on the promotion of world-class scientific research and cultural creation, and the recognition of talent.

The BBVA Foundation Frontiers of Knowledge Awards, funded with 400,000 euros in each of their eight categories, recognize and reward contributions of singular impact in physics and chemistry, mathematics, biology and biomedicine, technology, environmental sciences (climate change, ecology and conservation biology), economics, social sciences, the humanities and music, privileging those that significantly enlarge the stock of knowledge in a discipline, open up new fields, or build bridges between disciplinary areas. The goal of the awards, established in 2008, is to celebrate and promote the value of knowledge as a public good without frontiers, the best instrument to take on the great global challenges of our time and expand the worldviews of each individual. Their eight categories address the knowledge map of the 21st century, from basic knowledge to fields devoted to understanding and interrelating the natural environment by way of closely connected domains such as biology and medicine or economics, information technologies, social sciences and the humanities, and the universal art of music.

The BBVA Foundation has been aided in the evaluation of nominees for the Frontiers Award in Climate Change by the Spanish National Research Council (CSIC), the country’s premier public research organization. CSIC appoints evaluation support panels made up of leading experts in the corresponding knowledge area, who are charged with undertaking an initial assessment of the candidates proposed by numerous institutions across the world, and drawing up a reasoned shortlist for the consideration of the award committees. CSIC is also responsible for designating each committee’s chair across the eight prize categories and participates in the selection of remaining members, helping to ensure objectivity in the recognition of innovation and scientific excellence.